CI: Add ansys/actions/check-actions-security action and related fixes (#1575)

* ci: Pin actions used in workflow files with SHA

* ci: Use argument persist-credentials: false with actions/checkout

* ci: Avoid overly broad permissions for workflow jobs due to none being defined

* ci: Remove permissions for jobs that do not use secrets

* ci: Remove template expansions from inside job runs

* ci: Add actions security check to workflow

Author: ecoussoux-ansys